1. Field of the invention
The present invention relates to a monitoring system for plant operating conditions in which water quality data of such as nuclear power and thermal power plants are sampled in-situ and thereby diagnosis of high reliability is effected.
2. Prior Art
Japanese Patent Application Laid Open No. 58-51312 (1983) and U.S. Pat. No. 4,552,718 disclose monitoring devices for plant operation.
However, in the above Japanese Patent Application Laid-Open No. 58-51312 (1983) no method of obtaining information relating to water quality, no method of water quality evaluation information and no monitoring and controlling system of the plant in which the information from the respective water quality sensors is evaluated totally and water quality is monitored and controlled are disclosed. Further, U.S. Pat. No. 4,552,718 discloses in detail a method and system for plant operation control with regard to the status amount (output amount, cooling water level, temperature in reactor, etc.,) of a nuclear power plant operation. However, it does not disclose a water quality diagnosis and control system and technology which evaluate totally such as a sensing method of water quality itself, an evaluation method and a display system.
Japanese Patent Application Laid-Open No. 60-183595 (1985) discloses a plant operating method wherein observing pH (hydrogen ion concentration) of a nuclear reactor cooling water, pH of the cooling water is adjusted within a range between 7.0 and 8.5, but neither specify technology with regard to a pH sensor, nor clarify the relationship between the pH and other water quality information and further does not specify a display method during control.
ECP sensors (reference electrodes or corrosion potential sensor) in a high temperature and high pressure water is discussed in "Reference Electrode for PWR, Copyright 1987 Electric Power Research Institute, Inc." which is a comprehensive paper in recent years dealing the reference electrodes in a high temperature and high pressure water. The ECP sensor of Ag/AgCl (silver/silver chloride) which is employed for use in this paper has a structure wherein the silver/silver chloride regardless to an inner reference electrode or an outer reference electrode is immersed in a solution including Cl.sup.- (chlorine ion).
The Ag/AgCl electrodes are fundamental and representative reference electrodes for electrochemical measurement and these electrodes have a small temperature coefficient and have been used for the high temperature and high pressure water until now. However, under the severe environment such as the high temperature and high pressure water it was a problem that the sensor itself is deteriorated by potential variation due to the leakage of the Cl.sup.- ion accompanied with the deterioration of water seal in particular, there were no ECP sensors which were disposed in a nuclear reactor and had a life time level enduring the use in a periodic inspection interval.
The hydrogen ion concentration sensor in the high temperature and high pressure water is discussed in "Journal of Electrochemical Society, 132, 1866 (1985)" the problem is how to seal it or how to improve the durability of sensor itself which problem arises during disposing thereof in the reactor, wherein since the pH is measured by use of no liquid junction, isolating from the high temperature environment in a ceramic (of which porous ratio is near zero) cylinder and making use of the semiconductor property of the ceramic, its impedance becomes extremely high and there remain problems such as a counter measure to noise and an isolation method between the cylinder interior and the high temperature water environment.
With regard to an evaluation method of measured results and a display method, the above Japanese Patent Application Laid-Open No. 58-51312 (1983) also discloses a measure for displaying plant status amount during plant operation such as nuclear reactor pressure and cooling water level on the CRT of a computer as a specific screen image, however in this case again no technology with regard to sensing of the respective states and to monitoring of the water quality information is referred to, and further no indication is made on the measure which water quality information to be combined and how these to be evaluated.
Further no consideration on the sensor technology was made when controlling the water quality by monitoring the water quality and feeding back the water quality data to the control system, so that there was an actual problem that the water quality monitoring system and control system itself was impracticable due to the incredibility of the obtained data and the durability of the sensors. Therefore because of no credible sensors the system was limited to a plant operation and control based on the mechanical sides and status amount of the plant, no consideration from total point of view was made based upon an evaluation and plant method based on a technology which measures and controls the very water quality factors, an evaluation method based on a monitoring data display system and a displayed screen image, and other status amounts such as an abnormal sound of a pump and water quality status amount near the pump such as temperature and the results of water quality monitoring data, accordingly there was a technical problem that the plant control method could not operate the plant with necessary and sufficient information.
In Japanese Patent Laid-Open No. 58-215549 (1984), there is disclosed an electrochemical partitioned by a diaphragm and filled with electrolyte therein. However, for use in such environments as in a nuclear power plant or thermal power plant where stringent quality control of high temperature water is necessary, heat resistance and durability of the same are not satisfactory, confronting practical applications.
As disclosed in Japanese Patent Laid-Open No. 58-215549 (1983), means for separation and determination of dissolved hydrogen may be effective. In this case, however, because a selective hydrogen permeating membrane is required, there will still arise the like problem.
In the Electrochemical Method, John Willy & Sons, Inc. (1980) pp. 553-573, an electrochemical measurement apparatus for use in a nuclear power plant is described. However, there is no description on an electrochemical cell capable of being installed incore of a nuclear plant or in a piping system of a plant, and further having a low impedance reference electrode characteristic.